Background: Allergic reactions to measles, mumps, and rubella (MMR) vaccine are rare; some have been attributed to allergy to trace quantities of egg proteins. We report a 17-year-old female who had an anaphylactic reaction to MMR vaccine. A primary vaccination with MMR at age 15 months had been uneventful. She is not allergic to eggs; however, ear and throat pruritus and tongue swelling develop after she eats gelatin. MMR vaccine contains gelatin as a stabilizer.
Methods and results: Prick skin tests were positive to 1:10 wt/vol dilutions of MMR vaccine and gelatin but negative to egg. By immunoassay, her serum IgE antibodies were elevated to both MMR vaccine and gelatin, but not to isolated MMR antigens. IgE binding to the gelatin carrier could be inhibited in a dose-dependent fashion by addition of not only MMR vaccine but also gelatin from a variety of animal sources. Immunoblotting confirmed the presence of IgE antibodies to multiple gelatin components as well as to MMR vaccine components.
Conclusions: We conclude that the patient has an anaphylactic sensitivity to gelatin, and that her anaphylaxis to MMR vaccine was caused by the gelatin component. This sensitivity may explain other cases of MMR anaphylaxis.